Spark plug



OC 27, '1942. F A 05T- 2,299,924

` SPARK' PLUG Filed April 11, 1941 INVEN I OR.

Patented Oct. 27, 1942 UNITED. STATES RJJI'ENTv OFFICE4 2,299,924 j i n l SPARK PLUG 'Frederick A. 0st, Los Angeles, Calif. Application April 1-1, 1941, serial No. 398,929 7 claims. (or. 12s-169) This invention relatesV to spark plugs for internal combustion engines. of high compression and. :other types.` ThisA application is a continuation in part of my companion application filed June l0, 1940,` bearing Serial Number 339,647.

In addition to the various advantages attained by the construction set forth in mycompanion application the present improvement provides means` by which the spark plug terminals are adjustable apart tol produce a spark gap of any ,4 desired length Without bending, straining or haphazardly separating the terminals. 'Ihis feature combined with improvementsy by which theparts are leasily disassembled for` cleaning constitutes part of the features of. improvement of the present invention.

In the accompanyingr drawing yforming part of. this specification,` Fig. 1 is a side elevation of my improved spark plug; Fig.,2 is a longitudinal central section at increasedscale of the spark plug; Fig. 3 is an end'relevation; Fig. 4 is a side elevation` of the insulating core; Fig. 51 is an end View of the structure shown i'n Fig. 4 Fig. 6

`is a` perspective view of the adjustable spark gap terminal; Fig. rTis a side elevation of a` portion of the xed spark gap terminal, a portion t thereof being broken away and in section;` Fig. 8

is a side elevation `of `the vouter shell,` aA portion thereof beingbroken away and in section, showing the adjustable spark gap terminal therein,` and Fig. 9is a side elevation of the adjustable spark gap terminal, illustrating the varying `lengths of its legswhich coordinate with the heli-cal adjusting groove inrsaid shell. In illust tratingthe insulating core shown in Figs.` 4 and 5, solid black to indicate insulation is `eliminatedso as to distinguish more clearly the adjustable spark gap terminal lock groove 28,

t which otherwise would. be obliterated.y

Washer is adapted to be held to assist in producing a leakproof joint. Internally the body l of the shell has an inwardlytapering passage or shoulder I3, the outer` end portion being internally threaded at I4 for engagement by the eX- ternal threads of a bushing B. The inner end of the shell has acylindrical passage I4 coaxial 4with the shell andi corresponding in diameter with the inner end of the inwardly tapering pas.. sage I3. This passage` I4 has a helical adjusting groove I5 in its wallfwithwhich. the feet of the legs of an outer spark gap terminal C, to be hereinafter described are adapted to engage.

The tapering shoulder I3 forms a seat for the insulating core D. 'Ihis core resembles a tubular bodymade out of any suitable heat resisting elec- .trical insulating-material, such as moulded and compressed mica, having aconical inner end VI'I,

'the outer tapering surface of which corresponds with the inner conical passage I3V of the shell against which it is adapted to seat tightly when 'urged inwardly. The outer end portion of the core is of less diameter than the body I1 and resembles an. insulating shank or stem I8 of even diameter throughout its length. An annular abutment shoulder I9 is formed between the body I'Iy and shank I8.` An electrical, conducting spin- Udle 20 extends longitudinallyy and axially through the insulating core including its tapering shoulder and shank and has a circular inner' spark gap terminal head. E on its inner end and a nut terminal 22 on its `outer end by which i it is securedV inand holds the material comprising said core tightly compressed. The spindle 20, terminal head E and nut terminal 22 form one electrode of the spark. plug, the` opposite electrode` being provided by the. outer shell A. The terminal head E is dishedV in its outerend at 23 (seeFig. 7) -to form an annular -rim 24 which functions as an exposed electrical terminal of the spark gap. A wear ring 32A of metal or other suitable material is `placed over the shank I8 abutting the shoulder I9, against which the inner end of the bushing B presses when screwed into the shell, to tightly `seat the insulating core without abrading the insulating materiall and prevent leakage of gas.. A packing groove 33 a may be provided in the tapering shoulder ofthe core in which a sealing medium may be placed to doubly assure a tight connection between the shell and core. By unscrewingl and removing the bushing the insulating core and its spark gap terminal E can be removed and terminal C adjusted. Y

The exposed terminal C resembles a. spider frame, and is formed `from a ring shaped body 25`having exible longitudinal supporting legs 26, the latter rbeing struck outwardly on their free ends to form feet 21 which are concentric Y with` the .axis of the ring. The feet are adapted to rotatively engage the shell `in the helical groove |5 or abutment formed by the groove. The legs are varied in length in helical alignment to correspond with the pitch of the helical groove as shown in Figs. 8 and 9 so that the annular body of terminal C is held with its inner face in a plane parallel with the plane of the annular rim 24 of spark gap terminal E, irrespective of its longitudinally adjusted positions. To vary the gap between terminals C and E, the former is revolved in either direction desired, the helical groove and engaging feet 21 causing terminal C to move longitudinally inwardly toward or outwardly away from the inner fixed terminal E. To lock terminal C against rotation after it has been adjusted, the inner end of the body I1 of core D is provided with grooves 28 forming longitudinal abutment shoulders by which the free ends of the legs 26 are engaged when the core is seated tightly in the shell by the bushing. The inward sides of grooves 28 are adapted to press outwardly against the free ends of the legs of terminal C and hold the legs in firm contact against the wall of the outer shell. This action produces close electrical contact by terminal C with the shell and holds said terminalv` rigidly spaced longitudinally in adjusted position relative to terminal E. When it is desired to adjust the spark gap or disassemble the parts of the plug, the bushing is unscrewed and the core removed thus releasing terminal C and allowing it to be revolved by hand to either adjust its position longitudinally or remove it for cleaning or replacement.

As is disclosed in my companion application, the central opening |30 within the annulus 25 of spark gap terminal C and the recess 23 in the fixed spark gap terminal E produce a central duct by which the gas mixture enters and mushrooms radially through the spark gap and automatically cleans the spark gap terminals, thereby providing fresh and immediate contact of gas mixture in the gap for ignition and preventing fouling of the spark gap terminals. The dished terminal head E has the annular groove 3| in its side wall which tends to produce an inward, upward and outward eddy of the gas mixture or burning fuel to additionally scavenge the spark gap terminals and prevent fouling.

These features are added advantage for they increase the effectiveness and sureness of ignii tion. The terminal E, when desired, projects longitudinallyv slightly beyond the inner end of spark plug shell A, thus affording a better exposure, whereby the gas mixture has immediate contact with the spark. The terminal head E and terminal ring 25 afford a large surface exposure which increases the likelihood of producing an effective spark without any danger from interrupted ignition. The exposed portions of the spark gap terminals are also so proportioned and designed as to prevent over heating and detrimental oxidation of the parts. This advantage .is important, particularly in high compression engines.

In accordance with the patent statutes, I have described the principles of operation of my invention, together with the construction thereof which I now consider to represent the best ernbodiment thereof, but I desire to have it understood that the construction shown is only illustrative and that the invention can be carried out by other means and applied to uses other than those above set forth without departing from the spirit of the invention and within the scope of the following claims.

I claim:

1. A spark plug, comprising an outer elec.. trical conducting shell having an inner longitudinal tapering shoulder, an insulating core having a corresponding outer tapering shoulder adapted to seat against said `inner shoulder, a bushing threaded in said shell adapted to force said core longitudinally with its tapering shoulder tightly and immovably seated against the tapering shoulder of said shell, an electrical conducting spindle extending longitudinally through said core having a spark gap terminal on its inner end, and a spider frame having a spark gap terminal in juxtaposition to said spark gap terminal on said spindle and supporting means therefor forming an electrical conductor adjustably secured between and in contact with the adjacent surfaces of said core and shell to vary the gap between said spark plug terminals and electrically connect the spark gap terminal of said frame with said shell.

2. A structure as defined in claim 1 provided with locking means for holding the spider frame in adjusted position when the core is held seated by the bushing.

3. A spark plug, comprising, an outer electrical conducting shell having an inner longitudinal tapering shoulder, an insulating core having a corresponding outer tapering shoulder adapted to seat against said inner shoulder, a bushing threaded in said shell adapted to force said core longitudinally with its tapering shoulder tightly and immovably seated against the tapering shoulder of said shell, an electrical conducting spindle extending longitudinally through said core having a spark gag terminal on its inner end, and a spider frame comprising a spark gap terminal in juxtaposition to said spark gap terminal on said spindle and' electrical conducting supporting elements therefor, extending into the inner end of said shell, said shell having a helical abutment in its inner end by which the supporting elements are engaged to turn and vary the gap between said terminals and electrically connect the spider frame with said shell.

4. A spark plug, comprising, an outer electrical conducting shell having an inner longitudinal tapering shoulder, an insulating core having a corresponding outer tapering shoulder adapted to seat against said inner shoulder, a bushing threaded in said shell adapted to force said core longitudinally with its tapering shoulder tightly and immovably seated against the tapering shoulder of said shell, an electrical conducting spindle extending longitudinally through said core having a spark gap terminal on its inner end, and a spider frame having an annular spark gap terminal in juxtaposition to the spark gap terminal on said spindle and a plurality of supporting legs extending into the inner end of said shell, said shell having a helical abutment in the inner surface of its inner end with which the inner ends of said legs rotatively engage to adjust the gap between said spark gap terminals and electrically connect said annular spark terminal with said shell and said core having abutments engaging said legs to prevent the rotation of said spider frame when the core is held seated in said shell by said bushing,

5. In a structure las defined in claim 4, the inner ends of the legs of said spider frame being formed with outstanding feet engaging the shell in said helical groove and the abutments on the inner end of said core being formed by longitightly seated in said shell, an inner spark gap terminal on the inner end of said core havingv an electrical conductor leading outwardly through the core, an outer spark gap terminal swiveled in the inner end of said shell by a helical connection in juxtaposition to said inner terminal by which it is adjustable to vary the.

spark gap interval between said terminals, and

vabutment means on the inner end of said core ffor engaging said outer spark gap terminal to prevent the latter from turning when said core is held seated by said bushing in said shell.

7. A spark plug, comprising, an outer electrical conducting shell, an insulating core seated in said shell, a bushing for immovably holding said core tightly seated in said shell, an inner spark gap terminal on the inner end of said core having an electrical conductor leading outwardly through the core, and an outer spark gap terminal swiveled in said shell by a helical connection in juxtaposition to said inner terminal by which it is adjustable to vary the spark gap interval between said terminals, the inner end of said insulating core having means for engaging and locking the outer spark gap terminal to prevent the latter from turning when said core is immovably held seated in` said shell by said bushing.

FREDERICK A. OST. 

